Abstract: VAD (Velocity-Azimuth Display) technique can retrieve larger scale wind and divergence efficiently. Triple VAD(TVAD) and half VAD technique are an extension of VAD technique, they can get the large-scale mean wind information of different region in radar scan area. In this paper, the error analytic formula of expanded VAD technique (TVAD and half VAD) against VAD technique is obtained in theory. It is proved that harmonic analytic method can be used to calculate the first harmonic coefficient from half circle data accurately and from triple circle data approximately by error theory and simulating test and observed radar data fitting test. So the large-scale winds retrieved by half VAD technique have the same precision as the wind retrieved by VAD technique, and the large-scale winds retrieved by TVAD technique have some error. The error of the large-scale wind retrieved by TVAD technique has some relationship to initial phase of the fitting harmonic curve. The error of wind direction from TVAD technique is 0～20°, relative error of wind speed is 0～0.4. Simulated test of ideal harmonic dispersed data indicates that the average error of wind direction retrieved by TVAD is 16°, relative error of wind speed is 0.27, it is close to the error of conventional wind observation. The fitting test of Doppler velocity-azimuth profile illustrates that the fitting harmonic curve of half VAD technique and TVAD technique can give the characteristic of the large-scale wind field in the calculated area.

Key words: Doppler radar, VAD technique

摘要： 从理论上给出了扩展VAD相对于VAD的误差解析表达式，证明谐波分析方法可从半圆资料中精确地求出一阶富氏系数，因此半圆VAD方法计算出的大尺度风向风速和VAD方法有相同的精度。用1/3圆资料拟合简谐曲线所计算出的风向风速相对于VAD方法存在误差，其大小和简谐曲线的初位相有关，风向误差为0～27°、风速相对误差为0～0.4。理想简谐分布离散数据的模拟实验表明，TVAD的风向平均误差为16°、风速为0.27，与常规测风的误差相近。实际多普勒速度廓线的拟合实验说明半圆VAD技术和TVAD技术所拟合出的简谐曲线可以反映其所代表区域的风场大尺度特征。

关键词: 多普勒雷达, VAD技术